What is AWS CloudWatch?
Why Interviewers Ask This
This question tests conceptual clarity. Interviewers want to hear a precise, confident definition before moving to more complex AWS / Cloud Computing topics. It also reveals how well you can explain technical ideas to non-experts.
Answer
Amazon CloudWatch is AWS's observability service for monitoring AWS resources and applications. It collects data as metrics, logs, and events. Metrics: time-series data points. Default AWS metrics: EC2 CPU, network, disk (at 5-min intervals); detailed monitoring (1-min intervals, extra cost). Custom metrics: push from your app: aws cloudwatch put-metric-data --namespace "MyApp" --metric-name "OrdersPerMinute" --value 150. Key EC2 metrics: CPUUtilization, NetworkIn/Out, StatusCheckFailed. Note: memory and disk are NOT in default EC2 metrics — must use CloudWatch Agent. Alarms: monitor a metric and take actions when threshold breached. Actions: SNS notification, Auto Scaling action, EC2 action (stop, start, reboot, recover). States: OK, ALARM, INSUFFICIENT_DATA. Logs: CloudWatch Logs — collect, monitor, store, and access log files from: EC2 (via CloudWatch agent), Lambda, API Gateway, VPC Flow Logs, CloudTrail, ECS. Log groups → Log streams → Log events. Log Insights: query language for analyzing logs. Metric Filters: extract metrics from log patterns. Dashboards: customizable home pages of metrics and alarms. Events / EventBridge: respond to changes in AWS services (EC2 state change, S3 upload) or schedule events (cron). Trigger: Lambda, ECS task, SNS, SQS. Container Insights: metrics and logs for ECS and EKS. Synthetics: canary scripts for monitoring endpoints.
Common Mistake
Don't just define the term — demonstrate that you understand when to use it and when not to. Showing awareness of trade-offs is what separates average from strong AWS / Cloud Computing candidates.